Chemical mechanical planarization (CMP) is one process commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a substrate. CMP is effectively employed by providing contact between a feature-containing side of the substrate and a polishing pad by moving the substrate relative to a polishing pad while in the presence of a polishing fluid. Material is removed from the feature-containing side of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity. A polishing head is used to apply pressure to the substrate as the substrate is polished. The polishing head is rotated by a drive shaft, which is coupled to a polishing head motor.
Each type of substrate can often require a different pressure profile to best polish the substrate with a polishing head. A polishing head can include multiple pressurizable zones to apply the different pressures on different areas of a given substrate. Each pressurizable zone is coupled to a pressure supply line. The pressure supply lines are routed through a rotary union and a drive shaft to the polishing head. When the process specifies a different pressure profile, the pressure supply lines must often be re-routed to different pressure sources. Re-routing pressure supply lines is time consuming and consequently expensive. Furthermore, the limited space in the polishing head and the drive shaft places a constraint on the number of pressure supply lines that can be coupled to the polishing head. This constraint limits the number of pressurizable zones that can be included in a polishing head as well as the number of pressure profiles that a polishing head can apply.
Therefore, a need exists for an improved polishing system.